The present invention relates to internal combustion engines. In particular, the present invention relates to the lubrication of the crankshafts, and components associated with the crankshafts, of such engines.
Internal combustion engines have numerous moving parts that require lubrication to make long-term operation of the engines possible. A variety of techniques and mechanisms are employed by different internal combustion engines to assure that the required lubrication is properly provided to each of these parts.
One part of an internal combustion engine that requires lubrication is the crankshaft. In particular, lubrication is required at the interface between a crank pin of a crankshaft and a corresponding connecting rod that couples the crank pin to a respective piston. Additionally, lubrication is required along the main segments of the crankshaft itself, so that the crankshaft can freely rotate at its bearings with respect to the crankcase.
Additionally, often in single-cylinder internal combustion engines, special counterweights are coupled to the crankshaft to balance the forces generated by the reciprocation of the piston, which can otherwise result in undesirable vibration of the engine. In some embodiments of these engines, the crankshaft includes flanges that support coupling arms that are coupled to the counterweights. More specifically, the coupling arms have circular orifices that are supported upon eccentric rims of the flanges, such that the center axes of the circular orifices are displaced by a certain amount from the actual central axis of the crankshaft. As the crankshaft rotates, the flanges also rotate, while the rotational orientation of the coupling arms does not significantly change. Consequently, the center axes of the circular orifices rotate around the central axis of the crankshaft, and the coupling arms and counterweights move toward and away from the crankshaft. To allow the eccentric rims to rotate relative to the coupling arms, lubrication is required therebetween.
In order for lubrication to proceed along the length of the crankshaft, and particularly for lubrication to proceed to and past the crank pin, some conventional crankshafts include an oil circuit that includes a xe2x80x9cgun-drilledxe2x80x9d channel from a main crankshaft bearing to the crank pin.
Such conventional embodiments are difficult to manufacture. In particular, the gun-drilling of the channel from the main bearing to the crank pin along the crankshaft is a technically difficult and costly operation. Moreover, because gun-drilling is employed to create the channel in the crankshaft, cost-savings associated with casting of the crankshaft parts cannot be fully realized.
It would therefore be advantageous if a new crankshaft oil circuit could be developed in which one or more lubrication channels were formed by a simpler, more standardized and less costly operation than gun-drilling. It would further be advantageous if crankshafts employing the new crankshaft oil circuit could be more easily manufactured through the use of standardized, casted parts.
The present inventors have discovered a new crankshaft oil circuit by which lubricant can be provided along a first main segment of the crankshaft, then to the crank pin, and further back onto the other main segment of the crankshaft. The crank pin of the crankshaft, which is supported relative to the main segments of the crankshaft by a pair of crank arms, has an internal channel or oil galley that can be simply casted as part of the crank pin. Additionally, two flanges are employed that, in certain embodiments, have eccentric rims used to support counterweights with respect to the crankshaft. The flanges are positioned onto the crankshaft so that inner edges of the flanges abut outer sides of the respective crank arms and also so that outer edges of the flanges abut the respective main segments of the crankshaft.
Each of the flanges has first and second grooves along the respective outer and inner edges of the flanges, respectively. The first grooves extend along the respective main segments of the crankshaft, while the second grooves extend radially outward from the first grooves along the respective crank arms. The second grooves of the respective flanges in particular extend to cover respective ends of the oil galley. Because of the grooves, passages are formed between the ends of the oil galley and exterior portions of the main segments of the crankshaft (beyond the flanges). Lubricant can be communicated via these passages between the main segments of the crankshaft and the crank pin. In certain embodiments, an additional channel exists between the oil galley and an exterior surface of the crank pin, such that lubricant can also be provided to an interface between the crank pin and a connecting rod. The use of the flanges with grooves and casted crank pin eliminates the need for gun-drilling of channels, and makes it possible to use simple, standardized, and less costly parts to create the crankshaft oil circuit.
In particular, the present invention relates to a crankshaft that includes a crank pin, a first crank arm, a first main segment, and a first flange. The first crank arm is coupled to the crank pin and has a first outer side, and a first channel extends from within the crank pin to the first outer side. The first main segment is coupled to the first crank arm. The first flange has a first outer edge and a first inner edge, and is positioned on the first main segment so that the first outer edge abuts the first main segment. The first flange is further positioned so the first inner edge abuts the first outer side of the first crank arm. The first flange has first and second grooves along the first outer and inner edges of the first flange, respectively, and the first and second grooves form a first passage extending from the first channel to a first exterior portion of the first main segment, so that lubricant can flow between the exterior portion of the first main segment and the first channel via the first passage.
The present invention further relates to an internal combustion engine that includes a crankcase, a cylinder coupled to the crankcase, a piston within the cylinder, and a crankshaft supported by a pair of bearings of the crankcase. The crankshaft includes first and second main segments, a crank pin to which the piston is coupled by a connecting rod, first and second crank arms that respectively couple the crank pin to the first and second main segments, and means for conducting lubricant. The means for conducting channels the lubricant at least between a first point along one of the first and second main segments and the crank pin.
The present invention additionally relates to a method of distributing lubricant along a crankshaft. The method includes providing the lubricant at a first end of the crankshaft, allowing the lubricant to flow along a first main segment of the crankshaft from the first end of the crankshaft to a first passage, and guiding the lubricant by way of the first passage to a first channel, where the first channel extends at least partly through a crank pin of the crankshaft. The first passage is formed between a first crank arm coupling the crank pin to the first main segment, and a first flange abutting the first crank arm.